In the production of images on paper or other suitable media, referred to herein as paper, fuser surfaces which may comprise fuser rollers or fuser belts are commonly used to complete the copying or image making process, referred to herein as copying. Such fuser rollers are typically heated rollers which have a surface suitable for heating the toner to a desired temperature under pressure supplied by a pressure roller positioned to operably engage the paper between the fuser roller and the pressure roller to enhance, fix or otherwise improve an image on the paper. Fuser belts comprise a belt which may be heated which conveys the paper between a pressure roller and a backup pressure roller.
Such fuser surfaces typically have a length of approximately 15.5 inches, which enables the handing of 14-inch wide paper. Notwithstanding the use of fuser surfaces of this length, most paper processed through most copying machines is 11 inches in width. Accordingly, the middle portion of the fuser surface is used extensively and there is little use of the outside ends of the fuser surface.
To prevent sticking of the toner to the fuser surface, a release agent is typically supplied to the fuser surface by a wick roller. The wick roller may be independently driven or more commonly is driven by contact with the fuser roller or fuser belt. Typically a suitable pressure is applied to the mounts for the wick roller so that it engages the fuser surface with sufficient pressure to rotate the wick roller in response to the movement of the fuser surface. The wick roller deposits a pre-selected quantity of a release agent on the surface of the fuser surface prior to contact with each page of paper. The amount of release agent supplied is selected as that quantity necessary to prevent the toner from sticking to the fuser surface. Typically, release agents may be silicone oils which may contain various additives to facilitate their performance as an anti-sticking agent and are referred to herein as oil.
Since in many instances, the predominant paper size is 11 inch wide paper, many wick rollers have been adapted to oil only the central portion of the fuser surface, i.e., the middle 11 inch section of the fuser roller or fuser belt. This is accomplished by placing an oil impermeable coating over the ends of the length of the wick roller, outside a central section of the wick roller, so that no oil passes through the impervious coating. All of the oil then is released by the wick roller in a central portion of the wick roller, which corresponds, to the central portion of the fuser surface. While this has been effective to distribute the release agent in only the areas where it is needed, over long periods of time it has been observed that the absence of oil on the surface of fuser rollers in the end portions has led to non-uniform shrinking, non-uniform deformation and the like of the end portions. When the fuser roller surface becomes non-uniformly deformed it tends to adversely affect the paper handling ability of the fuser roller. Further if too much release agent is applied to the surface of the fuser rollers, or if supplied to the end portions of the fuser roller where it is not removed by the paper, it can result in non-uniform swelling of the fuser roller surfaces with a detriment to paper handling as a consequence.
Similar concerns exist with respect to belt fusers in that unused oil on the end portions of the fuser belt can accumulate to quantities which may result in dripping oil, degraded copy quality and the like.
Accordingly, in order to overcome these difficulties an improved method for controlling the distribution of fuser oil on a fuser surface has been sought.